This invention relates to a fuel feed device for an engine provided with electromagnetic valves capable of injecting fuel into the suction pipe, more particularly, to a fuel feed device for an engine capable of electronically controlling the fuel feed rate corresponding to the suction air rate.
It is known in conventional fuel feed devices for an engine to electronically control the fuel feed rate by driving an electromagnetic valve with pulse signals based on electric signals produced by electrical conversion of the suction air flow rate.
In general, the fuel feed rate required in full throttle operation at the maximum engine speed is 30 to 40 times the fuel feed rate at the idling engine speed as the air flow rate is 30 to 40 times the air flow rate at the idling engine speed.
Consequently, in a conventional fuel feed device with a single electromagnetic valve, the pulse width of the pulse signals need to be extremely small to smoothly operate the electromagnetic valve over the wide range corresponding to the engine operation from idling operation to maximum speed operation. Furthermore, when the pulse width is reduced, a large and expensive electromagnetic valve needs to be provided to assure highly responsive operation of the electromagnetic valve.